Conventional processes for forming semiconductor devices, such as CMOS devices, involve photolithographic patterning processes to illuminate regions of a photoresist layer, which can then be used to etch semiconductor device structures. A mask is used to define which regions of the photoresist layer are illuminated during the patterning process and which regions are not.
As semiconductor design rules shrink down to 32 nm technology node, or even further down to the 20 nm technology node, most critical levels of the manufacturing process are using polarized illumination for fine pitch patterning to obtain better image contrast, which can result in better resolution and edge control. For example, as can be seen in FIG. 13A, when polarized light 200 is directed through a mask (not shown) on quartz material (not shown), a pattern on the mask can be used to form Y direction structural lines 202 and X direction structural lines 204 on a substrate 206. However, the use of such polarized light only allows for very fine structures that extend in the Y direction (i.e. the same direction as the polarized light), as shown by the Y direction structural lines 202 in FIG. 13B. However, by using such a Y direction polarized light, structures that extend in the X direction do not have the same resolution as in the Y direction, as shown by the X direction structural lines 204 in FIG. 13C.
Thus, while polarization is one way to help to resolve patterns in smaller technology nodes, current methods sacrifice the resolution of patterns that extend in directions different from the direction of polarization. For example, for 20LPM (low power manufacturing) gate line, the minimum pitch allowed for a direction orthogonal to the polarization direction is three times wider than the polarization direction. For fine pitch in both directions, such as for a 20LPM metal 1 layer, double exposure, using two masks, must be employed.
A need therefore exists for methodology enabling the cost-effective and efficient photolithographic fabrication of semiconductor devices having high resolution in all directions using a single exposure with a single mask, the mask, and the method of fabricating the mask.